Integrated circuits (IC's) for applications such as smartcards, RFID tags, Pay-TV chips often contain a secret security key and carry out secret functions. The IC needs to be secure against attacks from the outside which aim at retrieving data there from. IC's may be subjected to both front-side as well as back-side attacks. In this description the “front-side” of a semiconductor device is defined as the side of the semiconductor device on which circuitry is provided. This side is also being referred to as the “first side of the substrate” in this description. Likewise, the “back-side” of the semiconductor device is defined as the side opposite to the front-side and this side is also being referred to as the “second side of the substrate” in this description. Back-side attacks may consist of various analysis techniques such as light or photon emission detection, thermal infrared detection, liquid crystal detection, voltage or electric field detection, and electro magnetic detection methods. Often these methods are used in combination with invasive attacks such as wafer thinning, laser cutting and heating, focused ion beam (FIB) techniques. Also light or laser flash methods are used from the back-side in order to force signals to flip. When any one of the above-mentioned techniques is used in combination with mathematical attacks, these attacks can be very powerful. Because a lot of the earlier-mentioned techniques are done from the back-side of the IC, it is essential that the back-side of these IC's are well protected. Physical attacks from the back side of an IC are becoming an increasingly important threat for IC's, and especially for bank cards. In the prior art, various protection schemes are disclosed.
Front side attacks are becoming less attractive as the number of metallization (interconnection) levels as well as their density increases with the technology nodes. This will shadow the circuitry of interest and, moreover, tiling (in-laid metal parts for CMP reasons) supports this effect even more.
US2001/003302 discloses an integrated circuit device comprising: a circuit which uses encryption, and an encapsulation packaging layer, in which the circuit is responsive to a magnetic field generated by the encapsulation to apply the encryption and/or decryption by reading the key there from, so that tampering with the encapsulation to gain access to the circuit causes the encryption and/or decryption to fail. The integrated circuit device comprises a matrix of sensors in a device substrate which are Hall effect sensors, which may comprise a thin film of Indium Arsenide in an opening in the upper layer of the chip. The encapsulation surrounds the device substrate on both sides, and comprises an epoxy resin matrix. In the epoxy resin matrix, a plurality of particles 360 are provided, of various sizes, shapes and/or magnetic permeabilities. These particles may be made out of Ni—Co—Fe alloy (i.e. a Ferrite alloy). A pair of plate-shaped permanent magnets are provided above and below the encapsulation layers, and bonded thereto by the epoxy resin. The magnets are arranged with their poles aligned in the same direction, which is conveniently perpendicular to the plates. Surrounding the plates and encapsulation is an outer casing of soft magnetic core material. The effect of the casing is to confine the magnetic field substantially within the casing, and to isolate it from external magnetic fields. It has a suitably high magnetic permeability (103 to 106 may be found suitable). The effect of the particles is to distort the magnetic field lines. Due to the non-uniformity of the distribution of the particles, the field lines are irregular in shape. Magnetic properties measured by the sensors will generally be different at each of the sensors, as described above. Any attempt to remove the outer shield will itself change the distribution of the magnetic field and therefore make it impossible to read the key.
A disadvantage of the known integrated circuit is that it constitutes a rather complex solution to data security, and that it is particularly not suitable for use in bank cards.